The RHEL 7 High Availability cluster packages are available on the RHEL 7 DVD ISO image. You could use following steps to install High availability packages offline using DVD ISO image:

Mount the DVD as in /media/RHEL71

$ cat /etc/yum.repos.d/localrhel7.repo 
[localrhel7]
name=RHEL7_Base
baseurl=file:///media/RHEL71
enabled=1
gpgcheck=0

[HA-Add-On]
name=HA-Add-On
baseurl=file:///media/RHEL71/addons/HighAvailability
enabled=1
gpgcheck=0

Save the above file and run yum repolist command which should list following two repositories along with any other repos or channels subscribed on the server:

$ yum repolist
[...]
repo id                        repo name                          status
HA-Add-On                      HA-Add-On                              25
localrhel7                     RHEL7_Base                          4,371
[...]